Review Question - QID 109097

A 69-year-old man presents to his primary care physician for trouble sleeping. He recently retired from working the day shift at a cemetery. When the patient retired, his goal was to finally be able to go out with his wife; however, he finds that he is unable to stay awake past 6 pm in the evening. His wife is disappointed that they cannot do any activities in the evening together. The patient has tried drinking caffeine but finds that it does not help. The patient’s wife claims that the patient seems to sleep peacefully, and the patient states he feels rested when he awakes. The patient has a medical history of irritable bowel syndrome which is managed with fiber supplements. His temperature is 98.6°F (37°C), blood pressure is 125/83 mmHg, pulse is 87/min, and respirations are 11/min. The patient’s neurological exam is within normal limits. Which of the following is the most likely diagnosis?